1. Field of the Invention
This invention relates to an articulated phonograph tonearm wherein the motion of the phonograph cartridge is controlled by a parallelogram-type of linkage structure.
2. Description of the Prior Art
The problem of minimizing distortion due to warped phonograph records is one that has received some attention by previous inventors. For example, U.S. Pat. No. 3,734,511 by Jacob Rabinow discloses a tonearm system in which the cartridge is supported by four strings so that the stylus automatically moves up and down in a straight line whenever a warped section of a record is played. See column 1, lines 23 through 34. Note also Rabinow U.S. Pat. Nos. 3,776,556 and 3,830,505 which dislose other tonearms which can operate upon warped records.
U.S. Pat. No. 3,485,501 to Baker discloses a tonearm using a four bar linkage. Note the abstract. The one drawback of that kind of structure is that it does not maintain the cartridge at a constant angle whenever the height of the record is varied.
Muller, U.S. Pat. No. 3,907,306 and German Pat. No. 2,432,639 disclose one kind of articulated tonearm, the Vestigal. The Vestigal is manufactured by Transcription, Penthouse G, 330 W. 58th Street, New York, N.Y. 10019. That type of tonearm appears to adjust to varying record heights, but includes structure quite different from the present invention. British Pat. No. 904,218 to Thorens is of interest in that it appears to disclose a relatively sophisticated and complicated mechanism including a plurality of linkages for supporting a phonograph cartridge. It is noted in particular that Thorens' patent refers to a first and second deformable parallelogram structure. However, the device otherwise appears to be quite different in function and shape from the present invention. The Dynavector is almost identical in principle to the Vestigal but has more damping. Many people consider the Dynavector to be one of the better tonearms on the market. The Dynavector is manufactured by Onlife Research, Inc., Tokyo, Japan and distributed in the U.S.A. by Audioanalyst, Inc., P.0. Box 262, Brookfield, Conn. 06804.